The invention relates to an apparatus on a drafting system of a spinning machine, especially a draw frame, carding machine, combing machine or the like, for weighting the drafting system rollers, having at least one pressure fluid cylinder with a piston which is acted upon by pressure fluid and is arranged so as to be axially movable inside a cylinder housing and from which a piston rod extends.
In a known apparatus (EP 1 428 914 A), a switching disc is frictionally mounted coaxially with the piston so as to be displaceable on the piston rod, which switching disc cooperates with a switch to determine the position of the piston. The switching disc is at least partly permanently magnetic in order to cooperate with an inductive sensor as a switch for determining the position of the piston. If a winding (lap) of fibre material then forms around the upper roller, the floating upper roller is pressed in the direction of the pressure fluid cylinder.
The presser rod of the pressure fluid cylinder making contact with the upper roller consequently moves in the direction of its retracted end position. When the presser rod is retracted, the switching disc, which is frictionally mounted thereon, closes the switch and the drafting system is switched off. The drafting system can then be opened manually and the lap removed. The drafting system can then be brought into the operating position again by closing the weighting arm.
It is an aim of the invention to provide an improved apparatus on a drafting system for determining the position of the piston with the piston rod.